1. Field of Invention
The invention relates to a backup electrical power system for household and structural appliances such as, but not limited to, refrigerators, freezers, furnaces and ancillary equipment, well pumps, and other like appliances.
2. Prior Art
All of the aforementioned appliances rely upon electrical power for operation. Primary electrical power, generated at a remote power generating plant, is provided to households and structures along power lines. On occasion, power outages occur for a variety of reasons including failure of a power grid or power transformer, power line damage resulting from vehicles colliding into poles carrying power lines, lightning strikes, and in many other ways. In the event of a power outage, household and structural appliances are deprived of their operating power and are rendered useless.
Through the years, many systems have been proposed, some of which have been, and are, presently marketed, to operate as a temporary replacement of the primary electrical power system during power outages. For example, a popular system has been gasoline or propane driven motor-generator sets. Solar energy and wind-driven generators have also been used, as have battery-operated inverters.
Gasoline operated motor-generator sets present serious problems, such as safety, fuel supply, and environmental pollution. For example, fuel storage is a serious safety consideration and may be in violation of fire codes under certain circumstances. Also, when the fuel supply is depleted, replenishing the fuel supply may not be possible due to the fact that sources of gasoline may not be able to pump gasoline because of the power outage.
Environmental considerations include the excessive amount of acoustical noise generated, and the exhausting of combustion products into the atmosphere from the engine. This is also true for propane fuel systems.
Except for the most expensive systems, most motor-generator systems require an external transfer switch that adds additional labor and material costs for installation. In addition, if no one is available during an outage to effect the transfer from primary power to backup power, and to start the motor-generator set, the advantage becomes moot. There are motor-generator sets that incorporate these necessities but their cost is prohibitive for most households.
Harvesting solar and wind energy are other sources, however both require an enormous physical structure in order to serve in a viable manner. Storage of energy by these generators requires expensive batteries and extensive electronic control equipment. And, these sources are very expensive, eliminating their practicability for the average homeowner.
The use of battery-operated DC to AC inverters is a viable alternative. Two directions have been taken to implement batteries. The uninterruptible power supply is one such direction. An uninterruptible power supply provides electrical power by means of a battery-driven DC to AC inverter that is always on line, that is, the uninterruptible power supply continuously generates power, even when primary electrical power is available, while a battery charger is continuously charging the battery. In this manner, in the event of a power outage, the uninterruptible power supply continues to provide power. This system is valuable to computer users since there cannot be loss of data during switchover that may take several milliseconds.
While this system eliminates the drawbacks of the systems described above, there are four disadvantages for using this system. First of all, batteries have a predictable lifetime depending upon the number of charge/discharge cycles and the depth of discharge, resulting in relatively early replacement. Secondly, for practical reasons of cost, size, and weight, the length of time an uninterruptible power supply can provide electrical power during a power outage is severely limited, certainly less than 15 to 30 minutes, at best, just long enough to save work in process before shutting down. The third reason is that the size and cost of such systems to endure a typical outage is enormous. Lastly, only limited power can be generated within the constraints of size, weight, and cost.
Unlike the uninterruptible power supply, a different type of battery-operated system has been proposed wherein the battery is on standby when primary power is available, and provides energy only during power outages. Heretofore, all these systems begin to generate backup power in the event of a power outage, providing electrical energy to all household and structural appliances simultaneously. This system, however, has a very limited operating time also, and requires greater electrical power to be generated in order to supply the peak power demands of appliances when supplied simultaneously. Peak power demands severely stress both the batteries and the backup power system, resulting in a shorter available operating lifetime of fully charged batteries.
None of the patents searched provide a means of maximizing the length of time batteries can provide power since they all begin generating power when a power failure occurs, and power is supplied to all appliances simultaneously.
3. Objects And Advantages
The above clearly defines the need for a system that can supply electrical power in the event of failure of the source of primary power, and doing so in a cost effective and viable way. Therefore, in the present invention, backup electrical power is delivered to household or structural appliances in a manner that circumvents all of the disadvantages cited above, and does so efficiently and effectively, maximizing the operating lifetime of fully charged batteries.